1. Field of the Invention
The present invention relates to a power supply system and a converter thereof, and more particularly to a direct-current (DC) converter composed of a pre-stage non-isolated conversion module and a post-stage isolated conversion module dedicated to resolve the issue of conventional DC converters being bulky due to use of transformer in each isolated converter in the conventional DC converters.
2. Description of the Related Art
With reference to FIG. 7, a conventional power supply system has an AC (Alternating Current) to DC converter 80, a DC converter 70 and two battery sets 73, 74. The AC to DC converter 80 has a set of AC input terminals and a set of DC output terminals. The set of AC input terminals is connected to a mains power. The set of DC output terminals is connected to a set of DC input terminals of the DC converter 70. The two battery sets 73, 74 are bridged over the set of DC input terminals to serve as backup power supplies. When the mains power is irregular, the DC converter 70 converts power of the battery sets 73, 74 into power with a desired voltage to continue supplying the converted power to a load.
When the foregoing power system is applied to a communication system, the DC converter 70 should be able to output power with negative voltage. With reference to FIG. 8, a DC converter 70 having negative output voltage has a first power conversion module 71, a second power conversion module 72, and two battery sets 73, 74. Each of the first power conversion module 71 and the second power conversion module 72 has a positive input terminal Vcom and a negative input terminal RTN1, RTN2. The positive input terminals Vcom of the first power conversion module 71 and the second power conversion module 72 are connected to a common positive terminal of the battery sets 73, 74. The negative input terminals RTN1, RTN2 are respectively connected to the negative terminals of the battery sets 73, 74. The first power conversion module 71 and the second power conversion module 72 respectively have two sets of output terminals, which are connected in parallel.
The foregoing DC converter employs a redundant structure. When one of the battery sets 73, 74 or one of the first power conversion module 71 and the second power conversion module 72 corresponding to one of the battery sets 73, 74 is faulty, the normal one of the first power conversion module 71 and the second power conversion module 72 can still supply power to the load to achieve the effect of redundant power supply.
Each of the first power conversion module 71 and the second power conversion module 72 of the foregoing DC converter is composed of an isolated converter, and the isolated converter is equipped with at least one transformer. To any communication system or server system, regardless of the system itself or the power supply therefor, how to reduce the size of the system and the power supply has long been a critical subject. However, due to the transformer required in each of the first and second power conversion modules 71, 72, size reduction naturally becomes a challenge to the foregoing DC converter.